The mobile phone has become a nearly ubiquitous personal computing device. Because it is quick to activate, universal, and frequently at hand, the mobile phone provides a convenient interface for an increasing number of standalone and/or embedded electronics in applications including system administration, home/office automation, environmental control, and others. For these purposes and others, a number of techniques have been developed to communicate between a computing system and a mobile phone or other mobile device. In addition to radio-band communications such as WiFi and BLUETOOTH® (a trademark of Bluetooth Special Interest Group), visible and near-visible light may be used to exchange data with a mobile device.